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Thermodynamics
05-27-2014, 07:27 AM
Post: #1
Thermodynamics
'ello!

According to thermodynamics hot goes to cold.
Why does it then feel like if cold is blowing in when you open a window?
Is it an illusion or a glitch in the Matrix?

?
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05-27-2014, 07:36 AM
Post: #2
RE: Thermodynamics
When wind blows past your face, your heat from your body transfers to the air. This is then blown away and replaced with more cool air.

Essentially, the wind is stealing your heat.

"Did you really think I was the demon? The Demon of Empire City?"
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05-27-2014, 08:23 AM
Post: #3
RE: Thermodynamics
(05-27-2014 07:27 AM)dnsk Wrote:  According to thermodynamics hot goes to cold.

your understanding of thermodynamics is incorrect.

high pressure flows into low pressure:
hot air - low atmospheric pressure (less dense)
cold air - high atmospheric pressure (more dense)

in an enclosed space, it may seem like the opposite is true as hot air will create a high pressure environment, but it's not. the hot air just want's to keep expanding and that creates pressure.

here's an experiment. take a plastic soda bottle and fill it half way with hot water then place that bottle in the fridge or freezer. check on it again in about half an hour to an hour and you will notice that the bottle is starting to collapse in on itself.

the hot air has cooled down and contracted and in the process, created a vacuum because cold air is more dense.

this is why hot air balloons work. the hot air is lighter since the hot air is less dense (lighter) than the surrounding cold air which is more dense (heavier).

the wing of an airplane operates in a slightly similar manner. the air above the wing has to move faster (spread apart, less dense) to keep up with the air below the wing (closer together, more dense) and that creates low pressure above the wing and high pressure below the wing... lift.

so, when you open your window, what you are experiencing is an equalization of pressure.

"Yeah. I understand the mechanics of it, shithead. I just don't understand how this is any less retarded than what I'm suggesting." - Kiley; Housebound.
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05-27-2014, 08:59 AM
Post: #4
RE: Thermodynamics
"Heat flows from a hotter to a colder body".
So when you open the (room) window, the heat is flowing out from the room. So you _feel_ less hot (or cooler).

Now, the outside and inside air could be at the same pressure but different temperature. Heat should be transferred.
So pressure difference can/will cause matter transfer, but I feel temperature difference must exist for heat transfer. Am still thinking about what I wrote :-)

Also if you were sweaty then the evaporation causes cooling (sensation in you).

So bottom line is heat energy is flowing out of you.
(Am asking myself so many questions now. haha)

Progress might have been all right once, but it has gone on too long -- Ogden Nash
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05-27-2014, 09:17 AM
Post: #5
RE: Thermodynamics
I see!

Thanks for the info. Now I'm more educated. Smile
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05-27-2014, 01:28 PM
Post: #6
RE: Thermodynamics
(05-27-2014 09:17 AM)dnsk Wrote:  I see!

Thanks for the info. Now I'm more educated. Smile

also...

in addition to thermodynamics, an other area of study concerning your op is continuum mechanics... primarily fluid dynamics (but really, fluid mechanics is more appropriate).

"Yeah. I understand the mechanics of it, shithead. I just don't understand how this is any less retarded than what I'm suggesting." - Kiley; Housebound.
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